The present invention relates to a floating type magnetic head support mechanism in a magnetic disk apparatus and, more particularly, to a magnetic head support mechanism in which a change in a floating amount of the magnetic head is suppressed upon access to the magnetic disk. The invention further relates to a magnetic disk apparatus provided with such a magnetic support mechanism.
For example, U.S. Pat. No. 4,620,251 proposes a support mechanism in which a flexible member of a gimbal of a magnetic head support mechanism extends in a direction perpendicular to an access direction of a slider. As disclosed in this patent, the flexible member is connected through a step portion to a coupling member provided in a surface substantially in parallel to the floating surface of the slider. The coupling member is coupled to a surface opposite to the floating surface of the slider.
Generally, in such a conventional mechanism, a distance between the floating surface and the coupling surface between the slider and the gimbal is longer than a distance between a center of gravity of the slider and the floating surface. For this reason, the slider is subjected to a dynamic moment to be rotated by an inertial force which acts upon the center of gravity of the slider during the acceleration or deceleration. As a result, the floating amount of the slider, i.e., the distance between the slider and the magnetic disk, is decreased.
Accordingly, it is impossible to suppress the flowing amount to a remarkable extent during the constant operation of the slider. This becomes a hindrance with respect to the amount of memory of the magnetic disk.
FIGS. 54 to 57 illustrate a floating decreasing amount of the slider during the access operation in the foregoing magnetic head support mechanism, with the amount being referred to as a sinking amount .DELTA.h of the slider.
As shown in FIGS. 54 and 55, the magnetic head support mechanism includes a load arm 200 (a load spring) and a gimbal 210 (a gimbal spring). As shown in FIG. 55, one end of the load arm 200 is connected by screws or the like (not shown) to a guide arm 230 connected to an access mechanism (not shown) and the other end holds the gimbal 210. One end of the gimbal 210 is connected to the load arm by spot-welding or the like, and the other end is coupled by adhesives or the like to a rear surface 22i of the slider 220, opposite to a floating top surface 222 facing a magnetic disk 240. The in-line type head support mechanism is characterized in that the slider 220 is provided with a floating rail (not shown) extending in the longitudinal direction of the load arm. FIG. 56 shows a model simulated to the magnetic head support mechanism upon the access operation from a mechanical and dynamic point of view. An application direction of acceleration .alpha. (260) is shown in FIG. 54 and a dimension of each part is shown in FIG. 55, wherein:
l.sub.1 =a distance from a center of a plate thickness of the load arm to a center of gravity G.sub.g of the load arm to a center of gravity G.sub.g of the load arm;
l.sub.2 =a distance from a center of a plate thickness of the load arm to a center of gravity G of the slider;
Y.sub.2 =a distance from the center of plate thickness of the load arm to the coupling surface between the slider and the gimbal, with the coupling surface being the rear surface of the slider; and
l.sub.w =a distance from the slider rear surface to the center of gravity G of the slider.
The characters shown in FIG. 56 are as follows:
k.sub.1 =a strength of a proximal spring of the load arm;
k.sub.2 =a strength of the spring of the gimbal;
k.sub.3 =a strength of an air spring, between the disk and the slider, formed by rotation of the disk;
.theta..sub.0 =a twist angle of the guide arm upon the access;
.theta..sub.1 =a twist angle of the guide arm upon the access;
.theta..sub.2 =a twist angle of the slider upon access, which angle is identical with the twist angle of the gimbal coupled to the slider. Namely, the twist angle .theta..sub.2 is a rolling angle of the slider. The angle causes imbalance (access sinking amount) in a floating amount of the slider floating rail between an inner circumferential side and an outer circumferential side of the disk. That is, as shown in FIG. 57, .DELTA.h is represented by the equation .DELTA.h =(y/2).multidot..theta..sub.2, where y=a width of the slider;
.theta..sub.3 =a twist angle of the disk upon the access operation (.theta..sub.0 and .theta..sub.3 becomes zero because of a high rigidity);
m.sub.1 =a mass of the load arm; and
m.sub.2 =a mass of the slider.
The deformation of each part upon access is given by the following equations in consideration of the equilibrium of the forces of the model shown in FIG. 56. EQU k.sub.1 .multidot..theta..sub.1 =m.sub.1 .multidot.l.sub.1 .multidot..alpha.-k.sub.2 .multidot.(.theta..sub.1 .div..theta..sub.2) -m.sub.2 .multidot.y.sub.2 .multidot..alpha. (1) EQU k.sub.2 .multidot.(.theta..sub.2 -.theta..sub.1)=m.sub.2 .multidot.(l.sub.2 -Y.sub.2).multidot..alpha.-k.sub.3 .multidot..theta..sub.2 (2)
From equations (1) and (2), the following relationship may be determined: ##EQU1##
Since k.sub.3 is larger than.sub.2 (k.sub.3&gt;&gt;k 2), equations (3) and (4) may be simplified as follows: ##EQU2##
The spring strengths, masses and lengths of the respective parts used are substituted into the right side of equation (4). The comparison among the magnitudes of the respective terms will be made. Incidentally, k, m, and l.sub.w are defined as follows: EQU k=1,700 mm/rad, k=50 gmm/rad, EQU l.sub.w =0.4 mm, m.sub.1 =44 mg, m.sub.2 =57 mg
The first term of the right side is: ##EQU3## From equation (5) and (6): ##EQU4## Equation (4) is further simplified as follows: ##EQU5##
If the width of the slider is y, and the sinking amount of the slider is .DELTA.h (floating decreasing amount due to the access acceleration), .DELTA.h is determined by the following equation: ##EQU6##
From equation (9), there are two methods of reducing the value .DELTA.h, namely, (a) decreasing y, m.sub.2, .DELTA., and l.sub.w and (b) increasing k.sub.3. Assuming that the slider configuration, the slider load, and the access acceleration are kept unchanged, in order to reduce .DELTA.h by improving the magnetic head mechanism, the decreasing of l.sub.w is effective to reduce .DELTA.h in equation (9).
However, in the conventional in-line type magnetic head support mechanism shown in FIG. 55, since the gimbal 210 is mounted on the slider rear surface 221, it is structurally impossible to reduce l.sub.w. Namely, due to the construction of the magnetic head support mechanism, it is impossible to reduce l.sub.w.